Molding composition



Patented Oct. 8, 1940 UNlTED STATES MOLDING COMPOSITION David E. Cordier, Toledo, Ohio, assignor to Plaskon Company, Incorporated, Toledo, Ohio, a corporation of Delaware No Drawing. Application September 13, 1938,

Serial No. 229,783

5, Claims.

The invention relates to plasticized formaldehyde-urea molding compositions.

Formaldehyde-urea molding compositions are thermosettingi. e., when molded under elevated 5 pressure and temperature they first soften and then harden at the molding temperature. A thermoplastic molding composition, in contrast. remains soft until the molded article has cooled. Although an article molded from a thermosetting l0 composition can be removed from the mold after a relatively short time and while the article is I still hot, an article molded from a thermoplastic composition cannot be removed from the mold until it has cooled, and thus hardened suflici'entl6 ly so that'it does not become blistered or distorted upon release of the pressure. The length of time for which a molding composition must be left in the mold isone of the factors that determines the cost of articles molded from the 20 composition. A composition that must be left in' the mold twice as long as another composition requires about twice as much molding equipment for the same volume of production, and hot-molding equipment is expensive.

Although the thermosetting character of formaldehyde-urea molding compositions is highly advantageous, the softening of such compositions that occurs in the mold before setting or hardening takes place is 'very important. A

go thermosetting composition that does not undergo proper initial softening in the mold cannot be molded properly. For example, an article molded from such a composition may not be properly homogeneous, and may consist of incompletely u softened granules cemented together. Granular. unfused structure, due to insufflcient softening of the-composition in the mold, is found most frequently in the central portions of relatively thick articles, such as knobs and handles.

Insuflicient initial fusing results in an unhomogeneous appearance of the finished article. such as a streaked surface in the case of a colored article. The surface appearance that is produced by failure of a molding composition to soften before setting is known as "dog skin. When a molding composition does not soften sufiiciently in the mold, bubbles or pockets of gas are frequently trapped, and produce flaws in the fin- E ished article.

o Although acid substances have been used as plasticizers in formaldehyde-urea molding compositions containing no cellulose, such substances cannot be used in a composition containing cellulose as a filler, because they render it unstable 55 and cause rapid deterioration. Formaldehydeurea molding compositions containing no cellu- I lose have not been found satisfactory for commercial use.

To be suitable for use as a plasticizer, a subgo stance should not be so alkaline as to'prevent the formaldehyde-urea molding composition from hardening in the mold. Substances that are highly soluble in water cannot be used as .plasticizers, because they seriously impair the resistant properties of a formaldehyde-urea resin.

Phenol has been suggested as a plasticizer for formaldehyde-urea molding compositions, but it is unsatisfactory because it imparts an undesirable color and odor to the compositions. More-- over,the color of a formaldehyde-urea composition containing phenol is so unstable that the compositionwouldhave to be handled in a rei'rigerated dark room to prevent the appearance of the 'molded articles from being spoiled. Toluene sulfonamides have been used or want of better plasticizers, but .their plasticizing effect is so slight that they are of little value.

Only substances that are soluble in formaldehyde-urea resin can be used as plasticizers, because insoluble substances bleed out of the resin and thus spoil'molded articles in which they are used. The substances that are soluble in form'- a'ldehyde-urea resin are very limited in number. Most of such substances seem to have a molecular structure similar to that ofthe resin; for example, certain urea derivatives are soluble in formaldehyde-urea resin. However, urea .de-

--rivatives in general do not have a plasticizing effect upon formaldehyde-urea molding compositions. Urea itself cannot be used as a plasticizer because of its deleterious eifect upon the product. The substances that are both soluble in formaldehyde-urea resin and capable of appreciably plasticizing a formaldehyde-urea molding composition are extremely rare.

The principal object of the invention is to provide formaldehyde-urea molding compositions containing novel'plasticizers. More specific objects and advantages are apparent from the description, which merely discloses and illustrates the invention and is not intended to impose limi- I tations upon the claims. I

A molding composition embodying the invention contains a plasticizer selected from the group consisting of organic compounds of the general formula ethyl, h'ydroxypropyl, hydroxybutyl or hydroxyamyl, and Y is H or X. Among these substances, the ethyl derivatives have the greatest plasticizing efi'ect, the propyl derivatives have less effect than the ethyl, the butyl derivatives have still less, etc.

The preferred plasticizers embodying the invention are organic compounds of the general formula in which Y is H, and X is H;CH (beta hydroxyethyl urea) or on CHr-JJH-Cflr (beta hydroxy n-propyl urea) and organic compounds of the general formula 0 NHz-PJN is H (n-butyl ureal, or -CI-Iz -CHz-CH2CI-Is (unsymmetrical dibutyl urea). These plasticizers should not be used in excessive amounts, because they tend to reduce the water resistance of products in which they are employed. A plasticizer illustrative of the general formula NHg-JNH-("3NHX is butyl biuret.

Beta hydroxy n-propyl urea may be prepared as follows: Urea and isopropanol amine om-im-cm-rm:

are heated under reflux until the evolution of ammonia ceases. The colorless viscous solution so produced sets to a crystalline mass, which can be ground with a small amount of acetone, and filtered. The crystals of hydroxypropyl urea so obtained may be recrystallized from alcohol.

A formaldehyde-urea molding composition of ,the usual type, consisting primarily of cellulosic material (40 to 50%) and a formaldehyde-urea reaction product, may be employed.

Example under a suitable pressure at a temperature of about 150 C.

Various applications of the invention may be devised to meet various requirements.

Having described my invention, I claim:

1. A thermosetting molding composition comprising a formaldehyde-urea reaction product and a plasticizer selected from the group consisting of organic compounds of the general formulae 0 o o x XNH0NH, X-NHC:NHX, NH:C:N

and

and

in which X is-a member of the group consisting of ethyl, propyl, butyl, amyl, hydroxyethyl, hydroxypropyl, hydroxybutyl and hydroxyamyl, said plasticizer being present in an amount that gives an appreciable softening action without materially impairing the water resistance of articles molded from the composition.

3. A formaldehyde-urea molding composition comprising beta hydroxyethyl urea as a plasticizer, said plasticizer being present in an amount that gives an appreciable softening action without materially impairing the water resistance of articles molded from the composition.

4. A formaldehydeurea molding composition comprising n-butyl urea as a plasticizer, said plasticizer being present in an amount that gives an appreciable softening action without materially impairing the water resistance of articles molded from the composition.

5. A formaldehyde-urea molding composition comprising n-butyl biuret as a plasticizer, said plasticizer being present in an amount that gives an appreciable softening action without materially impairing. the water resistance of articles molded from the composition.

DAVID E. CORDIER: 

